The invention relates to a rack or tooling for supporting parts in a heat treatment furnace.
A particular but non-exclusive field of application of the invention is that of tooling for supporting parts in a cementation furnace.
In the above field, the tooling most commonly used is made of metal. It suffers from the following main drawbacks:
the tooling is itself subjected to cementation and rapidly becomes brittle, which can give rise to a large amount of disorder in a furnace;
it must be bulky in order to avoid deforming excessively under load, since such deformation can in turn cause the supported parts to become deformed, requiring them to be rectified subsequently and consequently losing thickness in the cemented layer;
tooling that is bulky makes gas exchange more difficult and decreases loading efficiency, i.e. reduces the working fraction of the volume which it occupies by the parts to be treated;
violent thermal shock can cause the metal to be deformed or to break; and
the inevitable variations in dimensions that are of thermal origin make it impossible for the operations of loading and unloading parts and of handling the tooling to be robotized because of the unacceptable lack of accuracy in positioning.
It is already known, in particular from document EP 0 518 746-A to use a thermostructural composite material instead of a metal when making the sole plates of heat treatment furnaces. A plurality of sole plates can be provided and spaced apart from one another by spacers likewise made out of thermostructural composite material. The composite material used is a carbon/carbon (C/C) composite material or a ceramic matrix composite (CMC) material.
Nevertheless, that known loading device is poorly adapted to achieving optimum loading, of the kind that can be desired when a relatively large number of identical parts are to be treated. In addition, that device does not lend itself to robotization of the operations of loading and unloading the parts.
An object of the present invention is to remedy the above-mentioned drawbacks of prior art devices, and to this end the invention provides a rack made essentially out of thermostructural composite material and comprising: a baseplate; a partition extending upwards from the baseplate and comprising, for example, uprights with cross-members extending therebetween; and a plurality of support arms fixed to the partition and extending substantially horizontally therefrom to their ends which are free, the arms being disposed in substantially symmetrical manner on either side of the partition such that parts for treatment can be supported cantilevered out on said arms.
Because it is made of thermostructural composite material and because it has horizontal arms with free ends, the rack provides the positioning and accessibility accuracy required for robotizing the operations of loading and unloading the parts to be treated. Thermostructural composite materials such as C/C and CMC composites are characterized by their dimensional stability and by their bending strength, thus making it possible to load the parts in a cantilevered-out position.
In addition, such a rack can be made to be lightweight and open-structured, while providing a large amount of filling capacity. It is therefore easy to handle, provides great capacity for exchange with the parts to be treated, in particular during cementation or quenching operations, and presents high loading efficiency.
In addition, since the arms extend substantially symmetrically on both sides of the partition, loading can be balanced.
Furthermore, its structure is suitable for modular construction, making it easy from standard basic elements to adapt racks for parts of different dimensions and for different heat treatment installations.
According to a feature of the rack, pegs can be mounted on the support arms to mark locations for the parts to be treated. The parts can then be threaded or hooked onto the support arms if the parts have a through passage, or they can be suspended by resting on two adjacent arms.